Recently, an image forming apparatus such as an MFP (digital Multi Function Peripheral) has been commercially available such that a display screen equipped with a touch panel as a user interface (hereinafter, also referred to as UI) is made larger with various functions such as a preview function which are easier to be used and improved so as to be easily viewable. With the trend toward high functionality or multifunctionality for the MFP in this manner, a load on a CPU provided in the MFP of course increases.
When processing ability of the CPU becomes insufficient, operation of the MFP is suppressed so that a user gets stressed because, for example, preview display is not smoothly performed, scan performance is degraded, or the like. In this case, a high-performance CPU with high processing ability is attached to the MFP so as to be able to attempt load reduction, however, the high-performance CPU is generally expensive, thus causing cost increases of the MFP. Therefore, various techniques for effectively using the CPU without stressing a user out have been proposed.
For example, Japanese Laid-Open Patent Publication No. 2000-39930 describes an electronic device for monitoring a load on a CPU to change a clock. Such an electronic device is provided with a VCXO circuit capable of dynamically controlling a clock frequency; a CPU portion which operates with the clock; a program memory portion in which a program to operate is stored; and a program monitor control portion which optimally controls the clock by monitoring a progress state of the program, thereby being constituted so as to dynamically change the clock according to a software load of the CPU portion.
Here, in the case of processing a job with a high CPU load in the MFP, CPU utilization becomes nearly 100% in some cases. In this case, the CPU is occupied by the job processing, thus influencing operation of a UI in the MFP. For example, responsiveness of the UI is degraded so that preview display is stopped on the way, operation of screen switching and the like become awkward, or the like, thus heavily stressing a user out with such a state which is directly visible. Moreover, to the contrary, placing priority on the operation of the UI influences processing of a job with a high load, thereby, for example, temporarily stopping print processing by a printer or reading processing by a scanner, or the like, thus stressing the user out also in this case.
For addressing such a problem, with the technique described in Japanese Laid-Open Patent Publication No. 2000-39930, the clock is dynamically changed according to the load of the CPU, and operation of the clock is of course restricted. Therefore, in the case of exceeding restriction of the clock, it is impossible to suppress degradation of responsiveness of the UI without temporarily stopping the reading processing or the printing processing. Accordingly, the above-described problem is not solved with the technique of Japanese Laid-Open Patent Publication No. 2000-39930.